Phylum: Charophyta Family: Desmidiaceae
Xanthidium fasciculatum var. oronense West & G.S. West
West & West descibe this as 'An American variety', and note that the nominate is rare in Britain. The varietal epithet is named after Orono, a town in Maine, USA. Over 100 years later, both this and the nominate variety are rare in Britain. My finds have mainly come from acidic shallow-water lochs and lochans
References:
West, W. & West, G.S. (1912) A Monograph of the British Desmidiaceae, Volume 4
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands